Identification of immunoglobulin free light chains by mass spectrometry

Abstract

This document relates to methods for identifying one or more immunoglobulin free light chains in a sample using mass spectrometry. For example, this document relates to a method for identifying one or more immunoglobulin free light chains in a sample that includes (a) providing a sample; (b) subjecting the sample to a mass spectrometry technique to obtain a mass spectrum of the sample; and (c) identifying the presence of the one or more immunoglobulin free light chains.

What is claimed is: 
     
       1. A method for identifying one or more immunoglobulin free light chains in a sample, the method comprising:
 a. providing a sample, wherein the sample is a serum sample, a cerebrospinal fluid sample, or a whole blood sample; 
 b. enriching free light chains from the sample to obtain an enriched sample; 
 c. subjecting the enriched sample to a top-down mass spectrometry technique to obtain a mass spectrum of the sample; 
 d. identifying the presence of the one or more immunoglobulin free light chains; and 
 e. measuring the concentration of the one or more immunoglobulin free light chains in the sample. 
 
     
     
       2. The method of  claim 1 , wherein the sample is suspected to comprise an immunoglobulin free light chain. 
     
     
       3. The method of  claim 1 , wherein the one or more immunoglobulin free light chains are selected from the group consisting of free kappa light chains, free lambda light chains, and mixtures thereof. 
     
     
       4. The method of  claim 1 , wherein the immunoglobulin free light chain is a free kappa light chain. 
     
     
       5. The method of  claim 1 , wherein the method comprises identifying at least two types of free kappa light chains. 
     
     
       6. The method of  claim 1 , wherein the immunoglobulin free light chain is a free lambda light chain. 
     
     
       7. The method of  claim 1 , wherein the method comprises identifying at least two types of free lambda light chains. 
     
     
       8. The method of  claim 1 , wherein the one or more immunoglobulin free light chains comprises at least one of a glycosylated immunoglobulin free light chain, a cysteinylated immunoglobulin free light chain, and a glutathionylated immunoglobulin free light chain. 
     
     
       9. The method of  claim 1 , wherein the identifying the one or more immunoglobulin free light chains occurs in the presence of a polyclonal background. 
     
     
       10. The method of  claim 1 , wherein the method further comprises identifying at least one immunoglobulin free light chain dimer. 
     
     
       11. The method of  claim 1 , further comprising contacting the sample with a reducing agent prior to subjecting the sample to the mass spectrometry technique. 
     
     
       12. The method of  claim 11 , wherein the reducing agent is selected from the group consisting of dithiothreitol (DTT), reduced glutathione, β-mercaptoethanol, tris(2-carboxyethyl) phosphine hydrochloride, cysteine, 2-mercaptoethylamine, 3-mercaptopropionic acid, and mixtures thereof. 
     
     
       13. The method of  claim 11 , wherein the reducing agent is dithiothreitol. 
     
     
       14. The method of  claim 1 , wherein the method does not include contacting the sample with a reducing agent. 
     
     
       15. The method of  claim 1 , wherein the mass spectrometry technique is LC-MS/MS. 
     
     
       16. The method of  claim 15 , wherein the LC-MS/MS technique comprises a quadrupole time-of-flight mass spectrometer. 
     
     
       17. The method of  claim 1 , wherein the sample is a serum sample. 
     
     
       18. The method of  claim 1 , wherein the sample is from a single subject and the method further comprises diagnosing a disorder in the subject wherein the disorder is a plasma cell dyscrasia. 
     
     
       19. The method of  claim 1 , wherein the sample is from a single subject and the method further comprises diagnosing a disorder in the subject wherein the disorder is at least one of a multiple myeloma or a light chain amyloidosis. 
     
     
       20. The method of  claim 1 , wherein the sample is from a single subject and the method further comprises diagnosing a disorder in the subject wherein the disorder is at least one of multiple myeloma, monoclonal gammopathy of undetermined significance, B-cell chronic lymphocytic leukemia, Waldenstroms macrogloblinemia, amyloid light chain amyloidosis, or non-secretory myeloma. 
     
     
       21. The method of  claim 1 , wherein the sample is from a single subject and the method further comprises distinguishing an auto-immune response from a monoclonal gammopathy in the subject. 
     
     
       22. A method for identifying one or more immunoglobulin free light chains in a sample, the method comprising:
 a. providing a sample, wherein the sample is a serum sample, a cerebrospinal fluid sample, or a whole blood sample; 
 b. enriching free light chains from the sample to obtain an enriched sample; 
 c. contacting the enriched sample with a reducing agent; 
 d. subjecting the sample to a top-down mass spectrometry technique to obtain a mass spectrum of the sample; 
 e. identifying the presence of one or more immunoglobulin free light chains; and 
 f. measuring the concentration of the one or more immunoglobulin free light chains in the sample.